Production of lubricating oils from naphthenic crudes



March 5, 1963 E. M. HONEYCUTT 3,

PRODUCTION OF LUBRICATING OILS FROM NAPHTHENIC CRUDES Filed April 13,1960 Llghi Products Rechfy Treat co m o E N o m o m N Sn g 3 u.

INVENTOR.

EARL M. HONEYOUTT mph/43,0.

ATTORNEY United States PatentO 3,089,312 PRODUCTION F LUERHCATTNG GTLSFRQM. NAlHTl-IENEC CRUDES Earl M. Honeycutt, West (Ihester, Pa, assignorto Sun 50h Company, lhiladelphia, Pat, a corporation or New ersey FiledApr. 13, 1960, Ser. No. 21,964 3 Claims. (Q1. 2tl8-97) This inventionrelates to the production of lubricating oil from naphthenic crudepetroleum, and more particularly to a method involving the vapor phasetreatment of the lubricating oils with a liquid alkaline material.

It. is known in the art to produce lubricating oils from naphtheniccrudes' by flashing the oil to produce vapors and contacting the latterwith a liquid alkaline material. Following this contact, the hydrocarbonvapors are condensed to obtain a plurality of lubricating oildistillates having different viscosity and boiling range. This method ofproducing lubricating oils is advantageous since thepresence of thealkaline material in the distillation improves the color and colorstability of the distillates which are obtained. Also, the alkalinematerial reacts with naphthenic acids in the vapors to produce saltsfrom which the naphthenic acids can subsequently be recovered. The useof alkaline material in the distillation is further advantageous in thatit makes it unnecessary to provide separate treatments with alkalinematerial for each of the distillate products which are desired.

In order to perform this process for producing lubricating oils, a zoneis provided above the flash chamber, through which zone the liquidalkaline material is circulated. The temperature in this zone istypically in the range from 600 to 725 F, and the alkaline materialemployed is usually molten caustic soda. During the passage of vaporsthrough the zone, some of the hydrocarbon constituents of the vapors arecondensed. As a result of this condensation, and of reaction ofnaphthenic acids with caustic soda, the alkaline material asit leavesthe treating zone contains alkali metal naphthenates and liquidhydrocarbons in addition to the caustic soda. The desired concentrationsof components of the liquid material in the treating zone is maintainedby removing a drag stream externally of the treating zone and addingfresh caustic soda to the circulating stream to replace the materialremoved. Typically the alkaline material as it is withdrawn from thetreating zone contains 60 to 95 weight percent of liquid hydrocarbon, 3to 30 weight percent of alkali metal naphthenates. and 0.2 to weightpercent of alkali metal hydroxide. Naphthenic acids and hydrocarbon oilare usually recovered separately from the drag stream, and thehydrocarbon oil recycled to the treating zone to help maintain thedesired oil content.

It is important in the operation of this process that the viscosity ofthe alkaline material be controlled so that the alkaline material can besatisfactorily handled. In order to help maintain the viscosity at asatisfactory low level, the oil content of the alkaline material isregulated. When it is necessary to reduce. viscosity, the amount ofrelatively non-viscous oil in the alkaline material is increased. Thiscan be done for example by condensing more of the hydrocarbon vaporswhich are passed through the treating zone. This is disadvantageous,however, since it reduces the yield which is'obtained ofdesiredlubricating oil distillates. The problem of maintainingsatisfactorily low viscosity is particularly acute when the naphthenicacid content of the vapors passed through the treating zone isrelatively high. The naphthenate salts build up in such case to theextent that an excessive amount of relatively non-viscous oil must beprovided in order to maintain satisfactorily low viscosity.

In order to overcome these problems and disadvantages of the withdrawnmaterial is recirculated to-the-top of from 650 to 750 The flash zone isoperated under vacuum,

produce hydrocarbons an 'streamis removed through line 3 4 and APatented Mar.v 5, 1963 of prior art operation, the oil feed to theprocess is subjected according to the invention to a cracking operationbefore introduction into the. treating zone. The cracking is controlledto provide certain changes in the composition and properties ofcorresponding boiling range frac.- tions of the oil. The refractiveindex of the oil is increased by the cracking to obtain an increment inrefractive index which is within the range from 0.005 to 0.02. The ASTMacid number of the oil is reduced in the cracking to below 1.5 mg. ofKOH per gram, and usually to within the range from 0.1 to 1.5 mg. of KOHper gram. Usually the acid number prior to the cracking is at leastv 2mg. of KOH per gram; the acid number is usually not greaterthan 8 mg. ofKOH per gram. The acid number of the cracked product is usualy in therange from 5 to percent, preferably 10 to 50 percent, of the acid numberprior to cracking. Complete removal of naphthenic acids in the crackingis usually not feasible, but may be approached in some cases. The extentof conversion of the charge to. the cracking operation to gas, gasolineand coke is usually in the range from 5 to 30 weight percent, e.g. l to5 percent conversion to gas, 3 to 20 percent to gasoline and l to 7.5percent to coke;

The reduced acid number of the hydrocarbons as produced in the crackingcontributes to reduction of viscosity in the liquid alkaline material inthe subsequent treatment of the cracked vapors. The increased refractiveindex as a result of the cracking indicates an increased content ofaromatic hydrocarbons, resulting in the lubricating oil distillateshaving superior properties for various uses, e.g. as rubber processingoils.

The invention will be described more particularly in connection with theattached drawing which is a schematic flow sheet. of one embodiment ofthe invention.

Naphthenic crude petroleum is introduced through line 12 into toppingzone It) wherein gas oil and lighter fractions are removed as indicatedby line 14. The residue from the topping contains lubricating oilconstituents and is introduced, at a temperature for example in therange F.,,through line 16 into flash zone 18. usually at a to mm. of Hgabsolute,

pressure in the range from 40 be used, and lubricatthough other degreesof vacuum can ing oil constituents are vaporized and removed throughline 22. The residue from the flash distillation is re moved through theline 20.

The lubricating oil vapors areintroduced into cracking zone 24 whereinthey are contacted with a granular solid cracking catalyst at anelevated temperature in the range from 500 .to 750 F. Some cracking ofhydrocarbon constituents to lower boiling constituents occurs and alsosome decomposition of naphthenic acids, probably to d carbon dioxide asproducts. The cracked vapors are introduced through line 26 intodistillation and treating tower 30. i

In the treating zone of tower 30, the vapors are contacted with a liquidalkaline material which is passed downwardly over distillation trays inthe treating zone. When the alkaline material reaches the lowest tray inthe treating zone, it is removed through line 32. A drag subjected toconventional treatment for separate recovery of naphthenic acids andhydrocarbon oil. The alkaline material withdrawn through line 32contains liquid hydrocarbons, sodium naphthenates and sodium hydroxide.The bulk the treating zone through lines 28 and 35, fresh sodiumhydroxide being introduced through line 36 to replace that which reactswith naphthenic acids in the treating zone.

The treated hydrocarbon vapors pass upwardly into the rectifying sectionof tower 30, and distillate lubricatcatalysts such as bauxite, lithiumcarbonate, etc.

ing oils which are obtained in the rectifying zone are removed asindicated by the lines 40. The light products produced in the crackingare withdrawn from zone 3% through line 3-8 for suitable furtherprocessing as known in the art. Any liquid material at the bottom of thetower is removed through line 42.

As a typical example of operation according to the invention, Quiriquirecrude petroleum is topped to remove lower boiling material, and theresidue is vacuum ilashed to obtain a distillate having normal boilingrange of about 500 to about 1000 F. and having acid number of 6 mg. ofKOH per gram. This fraction is subjected to catalytic cracking. Theportion of the cracked products which boils above 400 F. has acid numberof less than 1.0 mg. of KOH per gram. The products of cracking arepassed through a treating zone containing sodium hydroxide, and thetreated vapors are rectified to obtain a plurality of lubricating oildistillates. A typical distillate obtained in this manner has normalboiling range of v about 808 to 865 F., specific gravity at 60 F. ofabout 0.980 and refractive index at C. of 1.5576.

By way of comparison, a lubricating oil distillate having boiling rangeof 815 to 877 F. and obtained in the same way except that the catalyticcracking operation is omitted, has specific gravity at 60 F. of 0.971and refractive index at 20 C. of 1.5437, as a result of the considerablylower aromatic hydrocarbon content of this distillate as compared withthe distillate obtained from the vapors which have been subjected tocatalytic cracking. Generally similar relationships between cracked anduncracked distillates are exhibited by lubricating oil distillateshaving different boiling ranges.

In the operation with the oil which has not been subjected to catalyticcracking, the high naphthenic acid content of the hydrocarbon vaporsresults in the formation of large amounts of sodium naphthenates in thetreating zone, and consequently the viscosity of the liquid material inthe treating zone is quite high, unless large amounts of oil arecondensed in the treating zone. These difiiculties are not encounteredin the case of the oil which has been previously cracked, since thenaphthenic acid content of the vapors is much less in this embodiment.

The higher aromatic content of the lubricating oil distillates obtainedfrom the oils which have been cracked results in better processabilityof the oils with rubber compositions, e.g. butadiene-styrene syntheticrubber compositions, and in other properties which make the oil .moredesirable in rubber compositions where relatively highly aromaticplasticizers or extenders are advanta geous.

Cracking catalysts which can be used in the process of the inventioninclude those granular solid cracking catalysts which are known for theconversion of relatively high boiling petroleum hydrocarbons torelatively low boiling hydrocarbons in the gasoline range. Suchcatalysts include the well-known synthetic silica-alumina,silicaalumina-magnesia, silica-alumina-chromia catalysts, etc., theactivated clay catalysts and other known cracking The syntheticsilica-alumina and the activated clay catalysts are preferred for useaccording to the invention.

The temperature in the cracking operation is in the range from 500 to750 F.', and preferably in the range -t'rom 600 to 700 F. Theseconditions provide the changes in composition and properties of the oilwhich give the benefical results according to the invention.

The cracking is preferably performed by passing the oil through astationary bed of the cracking catalysts. Typical liquid hourly spacevelocities are those in the range from 0.5 to 5. Preferably two beds areprovided which can be operated alternatively with one bed beingregenerated while the other bed is in service for the contact with thehydrocarbon oil. During the regeneration stage, carbon which has beendeposited during the cracking stage is burned from the catalysts in amanner which is well known in the art. Although the fixed bed type ofcracking is preferred, it is to be understood that the other known typesof cracking, such as the moving bed and fluidized catalyst types, canalso be employed.

In one embodiment of the invention, lubricating oil vapors are obtainedby vacuum flash distillation and con: tacted with the crackingcatalysts, then introduced into the treating zone, vacuum beingmaintained throughout these operations so that the lubricating oilhydrocarbons remain primarily in the vapor phase.

In another embodiment, the lubricating oil hydrocarbons are contacted inliquid or in mixed phase with the cracking catalyst, and the liquidcracked products are vacuum flashed to obtain vapors which areintroduced into the treating zone. in this embodiment, atmosphericpressure or elevated pressure, e.g. up to 15 p.s.i., can be employed ifdesired. Distillate or residual fractions can be charged to the crackingstep.

The cracked products may if desired be subjected to refining operationssuch as acid and clay treatment prior to introduction into the treatingzone for contact with alkali. On the other hand, the lubricating oildistillates recovered from the alkali-treated vapors can be subjected tosuch treatments if desired. However, such treatments are frequentlyunnecessary, either before or after th flowing downwardly in a treatingzone to remove naphthenic acids, condensing a portion of the lubricatingoil vapors in the alkali treating zone to maintain the viscosity of theliquid alkali at a suitably low level for circulation, and condensingand separating the treated vapors as lubricating oil distillates, theimprovement comprising contacting the naphthenic lubricating oilfraction, prior to its introduction to said treating zone, with agranular solid cracking catalyst at a temperature in the range of from500 to 750 F. to obtain a cracked product having refractive index in therange of from 0.005 to 0.020 greater than that of the original fractionand having an acid number of less than 1.5 mg. of KOH per gram, wherebythe quantity of lubricating oil vapors condensed to maintain viscosityis substantially reduced.

2. Process according to claim 1 wherein the lubricating oil fraction isobtained by flash distilling the crude petroleum, and wherein thevaporized fraction is contacted with the cracking catalyst and thenintroduced into the treating zone.

3. Process according to claim 1 wherein the cracking catalyst is asynthetic silica-alumina cracking catalyst.

References Cited in the file of this patent UNITED STATES PATENTS2,795,532 Honeycutt June 11, 1957 2,895,903 Johnson July 21, 19592,920,030 Thompson Ian. 5, 1960

1. IN A PROCESS FOR REFINING LUBRICATING OILS COMPRISING THE STEPS OFDISTILLING A NAPHTHENIC CRUDE OIL TO OBTAIN A NAPHTHENIC LUBRICATING OILFRACTION CONTAINING NAPHTHENIC ACIDS AND HAVING AN ACID NUMBER OF ATLEAST 2 MG. OF KOH PER GRAM, COUNTERCURRENTLY CONTACTING THE LUBRICATINGOIL FRACTION IN THE VAPOR PHASE WITH LIQUID ALKALI FLOWING DOWNWARDLY INA TREATING ZONE TO REMOVE NAPHTHENIC ACIDS, CONDENSING A PORTION OF THELUBRICATING OIL VAPORS IN THE ALKALI TREATING ZONE TO MAINTAIN THEVISCOSITY OF THE LIQUID ALKALI AT A SUITABLY LOW LEVEL FOR CIRCULATION,AND CONDENSING AND SEPARATING THE TREATED VAPORS AS LUBRICATING OILDISTILLATES, THE IMPROVEMENT COMPRISING CONTACTING THE NAPHTHENICLUBRICATING OIL FRACTION, PRIOR TO ITS INTRODUCTION TO SAID TREATINGZONE, WITH A GRANULAR SOLID CRACKING CATALYST AT A TEMPERATURE IN THERANGE OF FROM 500 TO 750* F. TO OBTAIN A CRACKED PRODUCT HAVINGREFRACTIVE INDEX IN THE RANGE OF FROM 0.005 TO 0.020 GREATER THAN THATOF THE ORIGINAL FRACTION AND HAVING AN ACID NUMBER OF LESS THAN 1.5 MG.OF KOH PER GRAM, WHEREBY THE QUANTITY OF LUBRICATING OIL VAPORSCONDENSED TO MAINTAIN VISCOSITY IS SUBSTANTIALLY REDUCED.